pebbledashing and crumbling mortar

i am having work done to my outside wall which is basically the wall down into my garden where a small shed is (probably an outside loo in the early 1900s. i have had a few builders in (10 to be exact) to comment on work that need doing on my garden. I have asked them to quote on taking off the pebbledash which has in some areas come off and replacing that with some smooth rendering. Only one of them pointed out that cos of the crumbling mortar that he can see - it might be a bigger job in the way that he would have to repoint it before rendering over. he has suggested that he could just tidy up what is there and render over this. As im trying to look at keeping costs down somewhere as works are over £7k i was just wondering if i went this way would there be problems later.

just realised i might have put this in the wrong section